Steering assembly for surgical robot

ABSTRACT

A surgical robot includes a robotic arm, a cart supporting the robotic arm and including a steering assembly. The steering assembly comprises wheels and a handle. The handle is moveable to a first position, a second position, and a third position. The steering assembly is configured such that the wheels allow the cart to roll in a longitudinal direction when the handle is in the first position, the wheels allow the cart to be roll a rotational direction when the handle is in the second position, and the wheels allow the cart to roll in a lateral direction when the handle is in the third position.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/793,076, filed Feb. 18, 2020, which is a continuation of U.S. patentapplication Ser. No. 15/256,273, filed Sep. 2, 2016, which claims thebenefit of and priority to U.S. Provisional Patent Application No.62/214,696, filed Sep. 4, 2015, and U.S. Provisional Patent ApplicationNo. 62/214,718, filed Sep. 4, 2015, all of which are hereby incorporatedby reference herein in their entireties.

BACKGROUND

The present invention relates generally to the field of carts fortransportation of a robotic device and stability of the robotic devicewhen in use.

Medical device carts may be used to transport a robotic device from onelocation to another. Traditional medical device carts have four wheels,two fixed front wheels and rear swiveling casters, which may provideadequate maneuverability during general transport, howevermaneuverability in an operating room has different needs. Space in theoperating room is limited which makes navigating the cart around theoperating room and into the proper position challenging. When pushingfrom a rear of the cart, controlling the direction of travel ischallenging because of the leverage required to direct the front wheels.The cart has to be backed up, pivoted, and moved back in. Sometimes thishas to be repeated several times until the position of the cart iscorrect. Sometimes, this requires handling the cart from a front endwhich may be in a sterile field of the operating room, which is notideal. Further, during transport, the cart may encounter various unevensurfaces (e.g., ramps, inclines, etc.) that may increase the loading onan individual wheel of the cart and potentially cause a rocking orfluttering condition.

SUMMARY

According to one exemplary embodiment, a portable surgical robotincludes a surgical device and a cart. The surgical device is coupled tothe cart. The cart includes a chassis, a mount coupled to the chassis, acarriage pivotally coupled to the mount, and a set of wheels. Thecarriage includes a first bracket positioned at a first lateral endthereof and a second bracket positioned at a second lateral end thereof.A first wheel of the set of wheels is coupled to the first bracket and asecond wheel of the set of wheels is coupled to the second bracket. Thecarriage is configured to pivot relative to the mount to prevent atleast one of (i) rocking of the portable surgical robot, (ii) flutteringof the first wheel, (iii) fluttering of the second wheel, and (iv)tipping of the portable surgical robot.

According to another exemplary embodiment, a portable cart includes achassis, a first wheeled mechanism coupled to a front portion of thechassis, and a second wheeled mechanism pivotably coupled to a rearportion of the chassis. The first wheeled mechanism and the second wheelmechanism facilitate maneuvering the portable cart. The second wheeledmechanism is configured to rotate relative to the chassis to prevent atleast one of (i) rocking of the portable cart, (ii) fluttering of thefirst wheeled mechanism, (iii) fluttering of the second wheeledmechanism, and (iv) tipping of the portable cart.

According to still another exemplary embodiment, a pivoting carriage fora cart includes a mount, a pivoting member, and a set of wheels. Themount has a housing that defines an internal cavity and a pivotaperture. The mount is configured to couple to a chassis of the cart.The pivoting member is disposed within the internal cavity of thehousing. The pivoting member includes a body having a first lateral endand a second lateral end, a first bracket positioned at the firstlateral end of the body, a second bracket positioned at the secondlateral end of the body, and a rod extending from the body. The rod ispositioned to engage the pivot aperture of the housing to therebypivotally couple the pivoting member to the mount such that the pivotingmember is pivotally coupled to the chassis of the cart. The set ofwheels includes a first wheel coupled to the first bracket and a secondwheel coupled to the second bracket.

According to yet another exemplary embodiment, a pivoting carriage for acart includes a frame member, a set of wheels, and a mount. The framemember includes a first bracket positioned at a first lateral end ofthereof and a second bracket positioned at a second lateral end thereof.A first wheel is coupled to the first bracket and a second wheel iscoupled to the second bracket. The mount is pivotably coupled to theframe member. The mount is configured to couple the pivoting carriage toa chassis of the cart. The frame member includes a pair of plates spaceda distance apart defining a cavity. The cavity is configured to receivethe mount and facilitate rotation of the carriage relative to the mount.

Alternative exemplary embodiments relate to other features andcombinations of features as may be generally recited in the claims.

BRIEF DESCRIPTION OF THE FIGURES

The disclosure will become more fully understood from the followingdetailed description, taken in conjunction with the accompanyingfigures, wherein like reference numerals refer to like elements, inwhich:

FIG. 1 is a front perspective view of a surgical cart, according to anexemplary embodiment;

FIG. 2 is a left rear perspective view of the surgical cart of FIG. 1 ;

FIG. 3 is a right rear perspective view of the surgical cart of FIG. 1 ;

FIGS. 4A-4D are various views of a pivoting carriage assembly of thesurgical cart of FIGS. 1-3 , according to an exemplary embodiment;

FIG. 5A is a perspective view of a chassis of the surgical cart of FIGS.1-3 with a locking mechanism in a transport configuration, according toan exemplary embodiment;

FIG. 5B is a perspective view of a chassis of the surgical cart of FIGS.1-3 with a locking mechanism in a braked configuration, according to anexemplary embodiment;

FIGS. 5C-5F are various cross-sectional views of a locking mechanismbeing reconfigured between a transport configuration and a brakedconfiguration, according to an exemplary embodiment;

FIG. 5G is a top plan view of the surgical cart of FIGS. 1-3 with alocking mechanism in a braked configuration, according to an exemplaryembodiment;

FIG. 6 is a perspective view of a steering assembly of the surgical cartof FIG. 1 , according to an exemplary embodiment;

FIGS. 7A-7B are various views of the steering assembly of the surgicalcart of FIG. 6 in a first configuration, according to an exemplaryembodiment;

FIGS. 8A-8B are various views of the steering assembly of the surgicalcart of FIG. 6 in a second configuration, according to an exemplaryembodiment;

FIGS. 9A-9B are various views of the steering assembly of the surgicalcart of FIG. 6 in a third configuration, according to an exemplaryembodiment;

FIG. 10 is a rear perspective view of a surgical cart, according toanother exemplary embodiment;

FIG. 11 is a perspective view of a chassis of the surgical cart of FIG.10 , according to an exemplary embodiment;

FIGS. 12A-12C are various views of a pivoting carriage assembly of thesurgical cart of FIG. 10 , according to an exemplary embodiment;

FIGS. 13-14B are various perspective views of a steering assembly of thesurgical cart of FIG. 10 , according to an exemplary embodiment;

FIGS. 15A-15B are various views of the steering assembly of the surgicalcart of FIG. 10 in a first configuration, according to an exemplaryembodiment;

FIGS. 16A-16B are various views of the steering assembly of the surgicalcart of FIG. 10 in a second configuration, according to an exemplaryembodiment; and

FIGS. 17A-17B are various views of the steering assembly of the surgicalcart of FIG. 10 in a third configuration, according to an exemplaryembodiment.

DETAILED DESCRIPTION

Before turning to the figures, which illustrate the exemplaryembodiments in detail, it should be understood that the application isnot limited to the details or methodology set forth in the descriptionor illustrated in the figures. It should also be understood that theterminology is for the purpose of description only and should not beregarded as limiting.

The portable surgical cart described herein may be used in any contextto maneuver and/or relocate a surgical device. The portable surgicalcart may also include various features to aid in the stability of thecart during relocation (e.g., on ramps, uneven ground, over door frames,etc.) and during use of a surgical device (e.g., during an operation ona patient, during use of an articulating arm, etc.). In one embodiment,the portable surgical cart includes a steering assembly that facilitatesmoving the cart in any of a forward direction, a backward direction, aturning direction, a lateral direction, and a rotational direction. Insome embodiments, the portable surgical cart includes a pivotingcarriage assembly configured to self-adjust on uneven surfaces toincrease stability of the portable surgical cart when stationary and/orin transit. In some embodiments, the portable surgical cart includes alocking mechanism configured to provide a support for the portablesurgical cart when stationary to allow for precise and stable use of asurgical device of the portable surgical cart.

According to the exemplary embodiment shown in FIGS. 1-17B, a portablecart system, shown as surgical cart 10, includes a body 20; a chassis100; a first wheeled mechanism, shown as wheel steering assembly 200,disposed at a front end 12 of the surgical cart 10; a second wheeledmechanism, shown as pivoting carriage assembly 300, disposed at a rearend 14 of the surgical cart 10; and a locking mechanism, shown as floorlock 400, disposed at the rear end 14 of the surgical cart 10.

As shown in FIGS. 1-3 and 10 , the body 20 of the surgical cart 10 iscoupled to the chassis 100. According to an exemplary embodiment, thebody 20 is removably coupled to the chassis 100 (e.g., fastened, etc.).In an alternative embodiment, the body 20 is fixed to the chassis 100.For example, the body 20 and the chassis 100 may be welded or glued toone another during construction of the surgical cart 10. In anotherexample, the body 20 and the chassis 100 may be a single, unitarystructure. The wheel steering assembly 200 includes a pair of wheels,shown as front wheels 202, and the pivoting carriage assembly 300includes a pair of caster wheels, shown as rear casters 302. The frontwheels 202 and the rear casters 302 facilitate moving the surgical cart10. According to an exemplary embodiment, the surgical cart 10 isconfigured to transport a surgical robotic device. In other embodiments,the cart is configured to transport a camera, a computer, a monitor,and/or any other device or component that may be used during a surgicalprocedure or medical monitoring. In alternative embodiments, the cart isconfigured for use as a guidance cart.

As shown in FIGS. 1-3 and 10 , the body 20 of the surgical cart 10 mayinclude a robotic device, shown as surgical device 30, a computingsystem 40, and a handle assembly 50. In some embodiments, the surgicalcart 10 does not include the surgical device 30. For example, thesurgical cart 10 may be a guidance cart and/or still another type ofcart (e.g., a cart configured to transport a camera, a computer, amonitor, and/or any other device or component that may be used during asurgical procedure or medical monitoring, etc.). In one embodiment, thebody 20 also includes various compartments (e.g., cabinets, drawers,etc.) configured to store various objects used in operation of thesurgical cart 10 (e.g., surgical tools, etc.). As shown in FIGS. 1-3 ,the surgical device 30 is coupled (e.g., fastened, etc.) to a mountinglocation 22 defined by the body 20. The surgical device 30 may be anysuitable mechanical or electromechanical structure. According to anexemplary embodiment, the surgical device 30 is an articulating arm(e.g., having three or more degrees of freedom or axes of movement,etc.). The computing system 40 may include various hardware componentsand software for operation and control of the surgical device 30. Thecomputing system 40 may be any known computing system but is preferablya programmable, processor-based system. For example, the computingsystem 40 may include a microprocessor, a hard drive, random accessmemory (RAM), read only memory (ROM), input/output (I/O) circuitry, andany other well-known computer component. The computing system 40 is maybe adapted for use with various types of storage devices (persistent andremovable), such as, for example, a portable drive, magnetic storage(e.g., a floppy disk, etc.), solid state storage (e.g., a flash memorycard, etc.), optical storage (e.g., a compact disc, etc.), and/ornetwork/Internet storage.

The computing system 40 may be communicably coupled to the surgicaldevice 30 via any suitable wired or wireless communication protocol(i.e., a physical interface). A physical interface may be any knowninterface such as, for example, a wired interface (e.g., serial, USB,Ethernet, CAN bus, and/or other cable communication interface) and/or awireless interface (e.g., wireless Ethernet, wireless serial, infrared,and/or other wireless communication system). A software interface mayenable the computing system 40 to communicate with and control operationof the surgical device 30. In one embodiment, the software interfaceincludes a utility that allows the computing system 40 to issue commandsto the surgical device 30. For example, the computing system 40 mayprovide a command to enter the surgical device into a specific mode(e.g., an autonomous mode, a haptic mode, a free mode, etc.). Thecomputing system 40 may be adapted to enable the surgical device 30 toperform various functions related to surgical planning, navigation,image guidance, and/or haptic guidance. For example, the computingsystem 40 may include algorithms, programming, and software utilitiesrelated to general operation, data storage and retrieval, computer aidedsurgery (CAS), applications, haptic control, and/or any other suitablefunctionality.

In one embodiment, the surgical device 30 is configured as an autonomoussurgical robotic system controlled by the computing system 40 to move asurgical tool to perform a procedure on a patient (e.g., for orthopedicjoint replacement, to perform bone cutting autonomously with a highspeed burr, etc.). In other embodiments, the surgical device 30 is ahaptic device configured to be manipulated by a user to move a surgicaltool to perform a procedure on a patient. For example, during aprocedure, the computing system 40 may implement control parameters forcontrolling the surgical device 30 based on a relationship between ananatomy of the patient and a position, an orientation, a velocity,and/or an acceleration of a portion of the surgical device 30 (e.g., asurgical tool, etc.). In one embodiment, the surgical device 30 iscontrolled to provide a limit on user manipulation of the device (e.g.,by limiting the user's ability to physically manipulate the surgicaldevice 30, etc.). In another embodiment, the surgical device 30 iscontrolled to provide haptic guidance (i.e., tactile and/or forcefeedback) to the user. “Haptic” refers to a sense of touch, and thefield of haptics involves research relating to human interactive devicesthat provide tactile and/or force feedback to an operator. Tactilefeedback generally includes tactile sensations such as, for example,vibration, whereas force feedback refers to feedback in the form offorce (e.g., resistance to movement, etc.) and/or torque (also known as“wrench). Wrench may include feedback in the form of a force, a torque,or a combination of a force and a torque.

In orthopedic applications, for example, the surgical device 30 can beapplied to the problems of inaccuracy, unpredictability, andnon-repeatability in bone preparation by assisting the surgeon withproper sculpting of bone to thereby enable precise, repeatable boneresections while maintaining intimate involvement of the surgeon in thebone preparation process. Moreover, because the surgical device 30 mayhaptically guide the surgeon in the bone cutting operation orautonomously perform the operation, the skill level of the surgeon isless critical. As a result, surgeons with varying degrees of skill andexperience are able to perform accurate, repeatable procedures.

As shown in FIGS. 1-3 , the surgical cart 10 includes a display device42 and an input device 44 disposed on the body 20 at the rear end 14 ofthe surgical cart 10. In an alternative embodiment, the display device42 and/or the input device 44 are otherwise positioned on the surgicalcart 10 or remote from the surgical cart 10 (e.g., mounted on a wall ofan operating room or other location suitable for viewing by the user,etc.). The display device 42 is configured as a visual interface betweenthe computing system 40 and the user. The display device 42 may becommunicably coupled to the computing system 40 and may be any devicesuitable for displaying text, images, graphics, and/or other visualoutput. For example, the display device 42 may include a standarddisplay screen (e.g., LED, LCD, CRT, plasma, etc.), a touch screen, awearable display (e.g., eyewear such as glasses or goggles), aprojection display, a head-mounted display, a holographic display,and/or any other visual output device. The display device 42 may be usedto display any information useful for a medical procedure, such as, forexample, images of anatomy generated from an image data set obtainedusing conventional imaging techniques, graphical models (e.g., CADmodels of implants, instruments, anatomy, etc.), graphicalrepresentations of a tracked object (e.g., anatomy, tools, implants,etc.), digital or video images, registration information, calibrationinformation, patient data, user data, measurement data, software menus,selection buttons, status information, and/or the like. The input device44 may enable the user of the surgical cart 10 to communicate with thesurgical device 30 and/or other components of the surgical cart 10(e.g., the wheel steering assembly 200, the floor lock 400, etc.). Theinput device 44 may be communicably coupled to the computing system 40and may include any device configured to enable a user to provide inputthe surgical cart 10. For example, the input device 44 may be, but notlimited to, a keyboard, a mouse, a trackball, a touch screen, a touchpad, voice recognition hardware, dials, switches, buttons, a trackableprobe, a foot pedal, a remote control device, a scanner, a camera, amicrophone, a joystick, and/or the like. In some embodiments, thesurgical cart 10 supplements or replaces direct visualization of asurgical site, enhances a surgeon's natural tactile sense and physicaldexterity, and facilitates the targeting, repairing, and replacing ofvarious structures in the body.

Referring to FIGS. 1-3 and 10 , the handle assembly 50 may increaseportability and maneuverability of the surgical cart 10. As shown inFIGS. 1-3 and 10 , the handle assembly 50 is positioned at the rear end14 of the surgical cart 10 and, in the embodiment shown, includes a pairof handles, shown as handgrips 52, and a handrail 54. The handgrips 52and/or the handrail 54 may facilitate maneuvering the surgical cart 10in at least one of a forward direction, a rearward direction, a lateraldirection (i.e., a sideways direction), and a rotational direction. Inalternative embodiments, the surgical cart 10 includes additionalhandles and/or handrails positioned around the body 20. In oneembodiment, the handle assembly 50 includes a single, continuousstructure that extends around the entire periphery of surgical cart 10to provide 360 degree handhold access for ease of maneuverability of thesurgical cart 10. In other embodiments, the handle assembly 50 includesa handrail positioned on one or both lateral sides of the surgical cart10 to facilitate pulling or pushing the surgical cart 10 from the side(e.g., in a lateral direction, forward direction, rearward direction,etc.). In other embodiments, the handle assembly 50 includes a handrailpositioned on the front end 12 of the surgical cart 10 to facilitatepulling or pushing the surgical cart 10 from the front end 12.

As shown in FIGS. 1-3, 5A-5B, and 10-11 , the chassis 100 includes afront portion 110, a rear portion 120, and a middle portion 130.According to an exemplary embodiment, the front portion 110 is coupledto the rear portion 120 via the middle portion 130 to create a single,continuous chassis 100 (i.e., a unitary structure). As shown in FIGS.5A-5B and 11 , the front portion 110 and the middle portion 130 of thechassis 100 define an inner volume 112. The inner volume 112 isconfigured to receive the wheel steering assembly 200 such that thewheel steering assembly 200 may be coupled to the chassis 100. The rearportion 120 of the chassis 100 defines a cavity 122. The cavity 122 isconfigured to receive the pivoting carriage assembly 300 such that thepivoting carriage assembly 300 may be coupled to the chassis 100.

As shown in FIGS. 4A-4D, the pivoting carriage assembly 300 includes aframe member, shown as pivoting carriage 310. The pivoting carriage 310includes a pair of brackets, shown as caster brackets 312. The casterbrackets 312 are configured to couple the rear casters 302 to thepivoting carriage 310. The rear casters 302 include an extension, shownas stem 304, that extends from a top portion thereof. The casterbrackets 312 are configured to receive the stems 304 of the rear casters302 to rotationally couple the rear casters 302 to the pivoting carriage310. In an alternative embodiment, the pivoting carriage 310 defines aflat mounting location and the rear casters 302 include a correspondingflat mounting plate configured to be fastened to the flat mountinglocation to couple the rear casters 302 to the pivoting carriage 310.According to an exemplary embodiment, the rear casters 302 arerotationally coupled to the pivoting carriage 310 such that the rearcasters 302 are free to rotate about a central axis thereof, shown asvertical axis 340. Thus, the rear casters 302 may freely rotate aboutvertical axis 340 as the surgical cart 10 is maneuvered. In someembodiments, the rear casters 302 include a brake to prevent rotation ofwheels of the rear casters 302 (i.e., aid in locking the surgical cart10 in place) and/or rotationally fix the rear casters 302 in a desireddirection (i.e., prevent rotation about the vertical axis 340). In analternative embodiment, the rear casters 302 are rotationally fixedrelative to the vertical axis 340 such that they are oriented in asingle direction (e.g., forward, etc.).

Referring still to FIGS. 4A-4D, the pivoting carriage assembly 300includes a mounting portion, shown as carriage mount 320. According toan exemplary embodiment, the carriage mount 320 is configured topivotably couple the pivoting carriage assembly 300 to the rear portion120 of the chassis 100. As shown in FIGS. 4A-4D, the carriage mount 320includes a top surface, shown as mounting surface 322, and sidesurfaces, shown as interaction surfaces 328. According to the exemplaryembodiment shown in FIGS. 4A-4D, the carriage mount 320 defines aplurality of apertures, shown as apertures 325, configured to receive acorresponding plurality of fasteners, shown as fasteners 326, thatextend from the mounting surface 322. In an alternative embodiment, thefasteners 326 are integrally formed along the mounting surface 322 ofthe carriage mount 320.

Referring back to FIGS. 5A-5B, the rear portion 120 of the chassis 100includes a plate, shown as mounting plate 124. The mounting plate 124defines a plurality of apertures, shown as apertures 126. The apertures126 are positioned to correspond with the fasteners 326 of the carriagemount 320 to facilitate coupling the pivoting carriage assembly 300 tothe chassis 100. According to an exemplary embodiment, the pivotingcarriage assembly 300 is recessed within the cavity 122 such that themounting surface 322 of the carriage mount 320 abuts a bottom surface ofmounting plate 124. In one embodiment, the apertures 126 are threadedsuch that an additional corresponding fastener (e.g., nut, etc.) is notneeded when the apertures 126 receive the fasteners 326 (e.g., bolts,etc.). In other embodiments, the fasteners 326 extend through theapertures 126 and receive corresponding fasteners (e.g., nuts, etc.) tocouple the pivoting carriage assembly 300 to the chassis 100. In stillanother embodiment, fasteners (e.g., nuts, etc.) are fixed (e.g.,welded, glued, integrally formed, etc.) to the mounting plate 124,positioned to align with the apertures 126 and receive the fasteners326.

Referring back to FIGS. 4A-4D, the pivoting carriage 310 defines a pairof apertures, shown as apertures 314. The apertures 314 are configuredto receive a rod, shown as pivoting rod 324, that extends from eachlongitudinal end of the carriage mount 320, thereby pivotably couplingthe carriage mount 320 and the pivoting carriage 310. The interactionbetween the apertures 314 and the pivoting rod 324 facilitates therotation of the pivoting carriage 310 about a longitudinal axis, shownas longitudinal axis 330. In some embodiments, the rotation of thepivoting carriage 310 about the longitudinal axis 330 is aided by alubricant and/or a bearing disposed between the apertures 314 and thepivoting rod 324.

As shown in FIGS. 4A-4D, the pivoting carriage 310 includes a pair ofplates, shown as plates 316, disposed on each lateral side of thecarriage mount 320. The plates 316 are spaced a distance apart to definea cavity, shown as pivoting gap 318. The pivoting gap 318 is configuredto receive the carriage mount 320 when the carriage mount 320 is coupledto the pivoting carriage 310 (e.g., rotationally coupled via thepivoting rod 324, etc.). According to an exemplary embodiment, thepivoting gap 318 is sized to facilitate the rotation of the pivotingcarriage 310 relative to the carriage mount 320.

As shown in FIGS. 4A-4C, the pivoting carriage assembly 300 includes alimiting member, shown as rotational stop 350, positioned on eachlateral side of the pivoting carriage 310. In other embodiments, thepivoting carriage assembly 300 includes a different number of rotationalstops 350 on each lateral side of the pivoting carriage 310 (e.g., two,three, etc.). As shown in FIGS. 4A-4C, the rotational stops 350 aredisposed along the plates 316. In one embodiment, the rotational stops350 are coupled to the plates 316 (e.g., welded, glued, fastened, etc.).In an alternative embodiment, the rotational stops 350 and the plates316 form a single, continuous structure (e.g., a unitary structure,etc.).

According to an exemplary embodiment, the rotational stops 350 areconfigured to limit the amount of rotation of the pivoting carriage 310relative to the carriage mount 320. By way of example, one of therotational stops 350 may contact a corresponding surface (e.g., a plate,etc.) of the rear portion 120 of the chassis 100 when the pivotingcarriage 310 reaches a pivoting travel limit (e.g., rotate two degreesabout the longitudinal axis 330, etc.). According to an exemplaryembodiment, the rotational stops 350 are sized to allow the pivotingcarriage 310 to rotate about the longitudinal axis 330 to the pivotingtravel limit which corresponds to a vertical displacement of at leastone of the rear casters 302 of approximately plus or minus 6 millimeters(mm) (e.g., a first caster 302 displaces upward a distance and a secondcaster 302 displaces downward the same distance, etc.). In otherembodiments, the rotational stops 350 are differently sized to allow thepivoting carriage 310 to rotate about the longitudinal axis 330 to adifferent pivoting travel limit (e.g., rotate one degree, rotate threedegrees, etc.) which corresponds to a vertical displacement of at leastone of the rear casters 302 of less than or greater than plus or minus 6mm (e.g., 4 mm, 8 mm, etc.). In some embodiments, the rear casters 302include a spring member to allow for additional or alternative verticaldisplacement to that provided by the pivoting carriage assembly 300.

In an alternative embodiment, the carriage mount 320 is laterally offsetfrom the longitudinal axis 330 (e.g., towards one of the rear casters302, etc.). Laterally offsetting the carriage mount 320 may facilitatevertically displacing one of the rear caster 302 a different distancethan the other rear caster 302 (e.g., one may displace a first distancein one direction and the other may displace a different distance in anopposing second direction, etc.). This configuration may be advantageousif the majority of the weight supported by the surgical cart 10 ispositioned towards one of the sides of the surgical cart 10. In yetanother alternative embodiment, the carriage mount 320 is omitted andreplaced by a central support structure configured to slidably receive acurved beam member. The curved beam member may be configured to slidablytranslate through the central support as the surgical cart 10 encountersvarious uneven surfaces causing the rear casters 302 to verticallydisplace. In still another alternative embodiment, the pivoting carriageassembly 300 includes a lateral plate that defines symmetrically angledslots positioned on each lateral side of the lateral plate. According toan exemplary embodiment, the symmetrically angled slots are configuredto receive and engage with pins. The engagement of the pins with thesymmetrically angled slots facilitates the rotation of the pivotingcarriage assembly 300 about a central axis thereof defined between thesymmetrically angled slots.

According to an alternative embodiment, the rotational stops 350 areomitted and the plates 316 are configured to limit an amount of rotationof the pivoting carriage 310 relative to the carriage mount 320. Therotation of the pivoting carriage 310 may be limited by an interactionbetween the interaction surfaces 328 of the carriage mount 320 and theplates 316. By way of example, the width of pivoting gap 318 (i.e.,based on the spacing between the plates 316, the distance between theplate 316 and the interaction surface 328) may define the amount ofrotation of the pivoting carriage 310 relative to the carriage mount 320(e.g., prior to all of the load from the surgical cart 10 beingtransferred through a single rear caster 302, etc.). For example, thelarger the width of the pivoting gap 318, a greater amount of rotationof the pivoting carriage 310 relative to the carriage mount 320 isallowed. Conversely, the smaller the width of the pivoting gap 318, alesser amount of rotation of the pivoting carriage 310 relative to thecarriage mount 320 is allowed.

As shown in FIG. 12B, the pivoting carriage assembly 300 includes aframe member, shown as pivoting carriage 360 (e.g., a pivoting bogie,etc.). The pivoting carriage 360 includes a main portion, shown as body362, having a pair of brackets, shown as caster brackets 364, with onepositioned at each lateral end of the body 362. The caster brackets 364are configured to couple the rear casters 302 to the pivoting carriage360. The caster brackets 364 are configured to receive the stems 304 ofthe rear casters 302 to rotationally couple the rear casters 302 to thepivoting carriage 360. In an alternative embodiment, the pivotingcarriage 360 defines a flat mounting location and the rear casters 302include a corresponding flat mounting plate configured to be fastened tothe flat mounting location to couple the rear casters 302 to thepivoting carriage 360. According to an exemplary embodiment, the rearcasters 302 are rotationally coupled to the pivoting carriage 360 suchthat the rear casters 302 are free to rotate about the vertical axis 340thereof. Thus, the rear casters 302 may freely rotate about verticalaxis 340 as the surgical cart 10 is maneuvered. In some embodiments, therear casters 302 include a brake to prevent rotation of wheels of therear casters 302 (i.e., aid in locking the surgical cart 10 in place)and/or rotationally fix the rear casters 302 in a desired direction(i.e., prevent rotation about the vertical axis 340). In an alternativeembodiment, the rear casters 302 are rotationally fixed relative to thevertical axis 340 such that they are oriented in a single direction(e.g., forward, etc.).

As shown in FIGS. 12A-12C, the pivoting carriage assembly 300 includes amounting portion, shown as carriage mount 370. According to an exemplaryembodiment, the carriage mount 370 is configured to pivotably couple thepivoting carriage assembly 300 to the rear portion 120 of the chassis100. As shown in FIGS. 12A-12C, the carriage mount 370 includes a body,shown as housing 372. As shown in FIG. 12C, the housing 372 of thecarriage mount 370 defines an internal cavity, shown as carriage cavity374. According to an exemplary embodiment, the carriage cavity 374 isconfigured to receive the pivoting carriage 360.

As shown in FIGS. 12A-12B, the pivoting carriage 360 includes a rod,shown as pivoting rod 366, that extends from the front and rear of thebody 362 of the pivoting carriage 360. As shown in FIGS. 12A-12C, thehousing 372 of the carriage mount 370 defines a pair of apertures, shownas pivot apertures 376. As shown in FIG. 12A, the pivot apertures 376are configured to receive the pivoting rod 366, thereby pivotablycoupling the pivoting carriage 360 to the carriage mount 370. Theinteraction between the pivot apertures 376 and the pivoting rod 366facilitates the rotation of the pivoting carriage 360 about alongitudinal axis, shown as longitudinal axis 390. In some embodiments,the rotation of the pivoting carriage 360 about the longitudinal axis390 is aided by a lubricant and/or a bearing disposed between the pivotapertures 376 and the pivoting rod 366.

As shown in FIGS. 11 and 12A-12C, the housing 372 of the carriage mount370 defines a plurality of apertures, shown as mounting apertures 378.As shown in FIG. 11 , the mounting apertures 378 are configured toreceive a plurality of fasteners (e.g., bolts, etc.), shown as fasteners384, to thereby couple the pivoting carriage assembly 300 (e.g., thepivoting carriage 360, the carriage mount 370, etc.) to the rear portion120 of the chassis 100.

As shown in FIG. 12C, the pivoting carriage assembly 300 includes alimiting member, shown as rotational stop 382, positioned within thecarriage cavity 374 of the housing 372 (e.g., disposed along an innersurface of a top portion of the housing 372, etc.), at each longitudinalend of the carriage mount 370. In other embodiments, the pivotingcarriage assembly 300 includes a different number of rotational stops382 positioned on each lateral side of the pivoting carriage 310 (e.g.,two, three, etc.). In some embodiments, the rotational stops 382 arecoupled to the housing 372 (e.g., welded, glued, fastened, etc.). Insome embodiments, the rotational stops 382 and the housing 372 form asingle, continuous structure (e.g., a unitary structure, etc.). In analternative embodiment, the rotational stops 382 are additionally oralternatively positioned on and/or coupled to the body 362 of thepivoting carriage 360.

According to an exemplary embodiment, the rotational stops 382 arepositioned to limit the amount of rotation of the pivoting carriage 360relative to the carriage mount 370. By way of example, one of therotational stops 382 may contact a corresponding surface (e.g., a topsurface, etc.) of the body 362 when the pivoting carriage 360 reaches apivoting travel limit (e.g., rotates two degrees about the longitudinalaxis 390, etc.). According to an exemplary embodiment, the rotationalstops 382 are sized to allow the pivoting carriage 360 to rotate aboutthe longitudinal axis 390 to the pivoting travel limit which correspondsto a vertical displacement of at least one of the rear casters 302 ofapproximately plus or minus 6 millimeters (mm) (e.g., a first caster 302displaces upward a distance and a second caster 302 displaces downwardthe same distance, etc.). In other embodiments, the rotational stops 382are differently sized to allow the pivoting carriage 360 to rotate aboutthe longitudinal axis 390 to a different pivoting travel limit (e.g.,rotate one degree, rotate three degrees, etc.) which corresponds to avertical displacement of at least one of the rear casters 302 of lessthan or greater than plus or minus 6 mm (e.g., 4 mm, 8 mm, etc.). Insome embodiments, the rear casters 302 include a spring member to allowfor additional or alternative vertical displacement to that provided bythe pivoting carriage assembly 300. As shown in FIGS. 12A-12C, thehousing 372 of the carriage mount 370 defines an aperture, shown asaperture 380, positioned at each end of the housing 372. According to anexemplary embodiment, the apertures 380 are positioned to prevent thecaster brackets 364 and/or the stems 304 from engaging the housing 372when the pivoting carriage 360 pivots about the longitudinal axis 390(e.g., when the pivoting travel limit is reached, etc.).

According to an exemplary embodiment, the pivoting carriage assembly 300and the front wheels 202 provide a quasi-four-point support for thesurgical cart 10 during transport and/or when stationary. For example,the pivoting ability of the pivoting carriage 310 and/or the pivotingcarriage 360 configures the surgical cart 10 to function as athree-wheeled cart (e.g., all of the loading is transferred to thechassis 100 through the carriage mount 320 or the carriage mount 370,etc.) when the pivoting travel limit is not reached and into afour-wheeled cart when the pivoting travel limit is reached (e.g., therotational stops 350 or the rotational stops 382 limit the rotation,etc.). Thus, the front wheels 202 and the pivoting carriage assembly 300provide a deterministic three-point support for the surgical cart 10(e.g., functions as a three-wheeled cart when the pivoting travel is notreached, etc.) for increased rocking resistance and caster flutteringresistance (e.g., relative to a traditional four-wheeled cart, etc.) andfour-point support (e.g., functions as a four-wheeled cart when thepivoting travel is reached, etc.) for increased stability (e.g.,improved tipping resistance, relative to a traditional three-wheeledcart, etc.).

According to an exemplary embodiment, the pivoting carriage assembly 300facilitates the self-adjustment of the surgical cart 10 while movingand/or stationary on an uneven surface (e.g., ramps, over door sills,over cords, into an elevator, etc.) to provide the three-point support.Traditional surgical carts with four-point support may lean whenencountering an uneven surface, transferring a greater amount of load toone side of the cart causing an increased risk for rocking of the cartor fluttering of a caster wheel. According to an exemplary embodiment,the rotation of the pivoting carriage 310 or the pivoting carriage 360relative to the carriage mount 320 or the carriage mount 370,respectively, (i.e., self-adjustment) advantageously prevents rocking ofthe surgical cart 10. By way of example, the self-adjustment may preventtransferring all of the loading from the surgical cart 10 onto one ofthe rear casters 302 (e.g., the load from the surgical cart 10 istransferred to an uneven ground surface substantially through both ofthe rear casters 302, etc.), which effectively prevents the surgicalcart 10 from rocking and/or one of the front wheels 202 and the rearcasters 302 from fluttering.

Traditional surgical carts with three-point support (i.e., three-wheeledcarts) may have an increased risk of tipping. According to an exemplaryembodiment, the pivoting carriage assembly 300 effectively provides afour-point support when the pivoting travel limit is reached toadvantageously prevent tipping of the surgical cart 10. Thus, thepivoting carriage assembly 300 eliminates rocking of the surgical cart10 and fluttering of the front wheels 202 and the rear casters 302,while still satisfying various regulatory requirements for tipping(e.g., IEC tipping standards, etc.).

Referring now to FIGS. 2-3, 5A-5G, 10-11, and 13 , the floor lock 400 isconfigured to stabilize the surgical cart 10 in place. The floor lock400 is configured to prevent movement of at least one of the rear end 14of the surgical cart 10 and the front end 12 of the surgical cart 10 ina lateral and/or a longitudinal direction when actuated (e.g., engagedwith a ground surface, etc.). According to the exemplary embodimentshown in FIGS. 2-3, 5A-5G, 10-11, and 13 , the floor lock 400 is amechanical mechanism actuated by an operator of the surgical cart 10. Inan alternative embodiment, the floor lock 400 is an electromechanicalmechanism that is actuated by an actuator (e.g., an electric motor,etc.) in response to receiving a command from the computing system 40(e.g., a command based on an operator input received by the displaydevice 42 or input device 44, etc.).

According to the exemplary embodiment shown in FIGS. 5A-5F, the floorlock 400 is selectively reconfigurable between a disengagedconfiguration, shown as transportation configuration 402 (shown in FIGS.5A and 5C), and an engaged, shown as machining configuration 406 (shownin FIGS. 5B and 5E) (e.g., such that the surgical cart 10 is in amachining mode, a park mode, a brake mode, etc.). The floor lock 400 maybe actuated from the transportation configuration 402 to the machiningconfiguration 406 in response to an operator of the surgical cart 10pressing down on a pedal 412. According to an exemplary embodiment, thefloor lock 400 is structured as a latching push-push mechanism thatrequires a single push to reconfigure the floor lock 400 from thetransportation configuration 402 to the machining configuration 406(e.g., a single push of the pedal 412 immobilizes an approximately 600pound cart, etc.), and vice versa. Advantageously, the floor lock 400eliminates the need for a ratcheting mechanism, a pumping mechanism,and/or an actuator (e.g., a hydraulic cylinder, an electric motor, etc.)to immobilize the surgical cart 10 with the floor lock 400 (e.g., theactuation of the floor lock 400 may be relatively easily provided by anoperator of the surgical cart 10, etc.). In an alternative embodiment,the floor lock 400 is configured as a push-pull mechanism such that bypushing on the pedal 412 causes the floor lock 400 to engage a groundsurface and lifting on the pedal 412 cause the floor lock 400 todisengage from the ground surface. In yet another alternativeembodiment, the floor lock 400 includes a first lever configured toengage the floor lock 400 with a ground surface and a second leverconfigured to disengage the floor lock 400 from the ground surface.

As shown in FIGS. 5A-5F, the floor lock 400 includes a first member,shown as brake pedal 410, and a second member, shown as brake 420. Thebrake pedal 410 includes an actuation surface, shown as pedal 412,coupled to a pair of arms, shown as arms 414. According to an exemplaryembodiment, the pedal 412 is foldable (e.g., for storage, to move out ofthe way, etc.). By way of example, the pedal 412 may be pivotablycoupled to the arms 414 with rotational stops that facilitateselectively positioning the pedal 412 between a stowed position and anoperational position. The arms 414 may define a slot configured toreceive a limiter of the pedal 412. The slot may define the motionthrough which the limiter, and thereby the pedal 412, may travel. Asshown in FIGS. 5C-5F, the arms 414 are rotationally coupled to thechassis 100 via a fastener, shown as hinge 416. As shown in FIGS. 5A-5F,the brake 420 includes an arm, shown as brake arm 422, and a pad, shownas brake pad 424, coupled to the brake arm 422. As shown in FIGS. 5C-5F,the brake arm 422 is rotationally coupled to the chassis 100 via afastener, shown as hinge 426. As shown in FIG. 5B, the floor lock 400includes an actuator, shown as brake actuator 430. The brake actuator430 may include a gas cylinder, a hydraulic cylinder, a coil spring, orthe like. The brake actuator 430 is configured to couple the brake pedal410 to the brake 420.

As shown in FIGS. 5A-5F, the floor lock 400 further includes a firstlever, shown as latching lever 440; a guide block, shown as cam block450; a second lever, shown as extension lever 460; and a pair oflinkages, shown as lift linkages 470. In some embodiments, the floorlock 400 includes legs (e.g., one, two, three, etc. legs), shown asfront chassis legs 480, positioned at the front end 12 of the chassis100. As shown in FIGS. 5C-5F, a first end of the latching lever 440 ispivotably coupled to the brake pedal 410 via a fastener, shown as hinge418, and an opposing second end of the latching lever 440 is slidablycoupled within a slot, shown as cam track 452, defined by the cam block450. The opposing second end of the latching lever 440 may also becoupled to a first end of a second lever, shown as extension lever 460.An opposing second end of the extension lever 460 is coupled to a firstend of the lift linkage 470. The lift linkage 470 includes a firstmember, shown as rotational linkage 472; a second linkage, shown asguide linkage 474; a third linkage, shown as cylinder 476; and a fourthlinkage, shown as rod 478. As shown in FIGS. 5A-5F, the floor lock 400includes a bracket, shown as bracket 479. The bracket 479 is configuredto couple an opposing second end of the lift linkage 470 to the body 20of the surgical cart 10. According to an exemplary embodiment, the liftlinkage 470 is configured to facilitate lifting the front wheels 202such that the front portion 110 of the chassis 100 kneels (i.e., akneeling feature) until the front chassis legs 480 contact a groundsurface 600. In an alternative embodiment, the lift linkage 470 isconfigured to facilitate the extension of the front chassis legs 480such that the front chassis legs 480 lift the front portion 110 of thechassis 100 such that the front wheels 202 no longer engage the groundsurface 600. According to an exemplary embodiment, the lift linkages 470are or include gas springs.

As shown in FIGS. 5A and 5C, the floor lock 400 is configured in thetransportation configuration 402. The brake pad 424 and the frontchassis legs 480 do not come into contact with the ground surface 600 inthe transportation configuration 402, facilitating transporting and/ormaneuvering the surgical cart 10 freely. As shown in FIG. 5D, a user mayapply a downward actuation force on the pedal 412, indicated bydirectional arrow 490, such that the arms 414 rotate downward abouthinge 416 and reconfigure the floor lock 400 into an intermediateconfiguration 404 from the transportation configuration 402. Theactuation of the brake pedal 410 causes the brake arm 422 of the brake420 to rotate about the hinge 426 (e.g., via the brake actuator 430,etc.) such that the brake pad 424 engages the ground surface 600. Theactuation of the brake pedal 410 to the intermediate configuration 404further causes the opposing second end of the latching lever 440 tofollow along the cam track 452 in a first rotational direction (e.g.,counter-clockwise, etc.), which thereby causes the extension lever 460to extend and engage the rotational linkage 472 such that the rotationallinkage 472 rotates. The rotation of the rotational linkage 472 causesthe guide linkage 474 and the rod 478 to translate (e.g., verticallyupward, etc.) such that the rod 478 slidably translates within thecylinder 476. According to an exemplary embodiment, the translation ofthe rod 478 corresponds with a vertical displacement of the front wheels202 such that the front portion 110 of the chassis 100 lowers (i.e.,kneels) until the front chassis legs 480 engage the ground surface 600.In an alternative embodiment, the translation of the rod 478 correspondswith a vertical displacement of the front chassis legs 480 such that thefront portion 110 of the chassis 100 rises until the front wheels 202disengage from the ground surface 600.

As shown in FIG. 5E, the user may stop applying the downward actuationforce on the pedal 412 such that the arms 414 rotate upward about thehinge 416, as indicated by directional arrow 492, configuring the floorlock 400 into the machining configuration 406. By releasing the brakepedal 410, the latching lever 440 proceeds along the cam track 452around a lip, shown as latching lip 454 (see, e.g., FIGS. 5C-5D). Thelatching lip 454 holds the latching lever 440 in place such that thefloor lock 400 remains in the machining configuration 406 (e.g., withoutan external force being applied by an operator, etc.). It should benoted that FIGS. 5D-5E are separated for illustrative purposes only. Inpractice, reconfiguring the floor lock 400 of the surgical cart 10 fromthe transportation configuration 402 to the machining configuration 406requires a single actuation motion (e.g., pressing down on the pedal 412and then releasing, etc.).

As shown in FIG. 5F, a user may apply a downward actuation force on thepedal 412, indicated by directional arrow 494, such that the arms 414rotate downward about hinge 416 and reconfigure the floor lock 400 intoa disengagement configuration 408 from the machining configuration 406.As shown in FIG. 5F, applying a downward force onto the pedal 412 whenin the machining configuration 406 causes the opposing second end of thelatching lever 440 to disengage from the latching lip 454. Thedisengagement of the opposing second end of the latching lever 440 fromthe latching lip 454 allows the latching lever 440 to follow along thecam track 452 in a second rotational direction (e.g., clockwise, etc.)to return the floor lock to the transportation configuration 402. Forexample, following the application of the downward force, a user mayremove the force from the pedal 412 (e.g., release the pedal 412, etc.)such that the latching lever 440 moves in the second rotationaldirection around the cam track 452. Thus, the brake pedal 410 rotatesabout the hinge 416 and returns to the position shown in FIG. 5C (i.e.,the transportation configuration 402), thereby causing the brake 420 torotate about the hinge 426 such that the brake pad 424 disengages fromthe ground surface 600. Further, the extension lever 460 retracts,thereby causing the guide linkage 474 and the rod 478 to translatevertically downward such that the rod 478 slidably translates out fromthe cylinder 476. In turn, the front wheels 202 extend downward toengage the ground surface 600, lifting the front portion 110 of thechassis such that the front chassis legs 480 disengage from the groundsurface 600.

As shown in FIGS. 11 and 13 , the lift linkages 470 (e.g., the cylinder476 and the rod 478, etc.) may be replaced with a suspension element,shown as coilover 482. The coilover 482 includes a shock absorber, shownas shock 484, and a resilient member, shown as coil spring 486,encircling the shock 484. According to an exemplary embodiment, thecoilover 482 is configured to provide controlled dampening as the frontportion 110 of the chassis 100 kneels and lifts. In other embodiments,the floor lock 400 includes a plurality of coilovers 482 (e.g., two,three, etc.).

According to an exemplary embodiment, the engagement of the brake pad424 with the ground surface 600 substantially prevents movement of therear end 14 of the surgical cart 10 (e.g., in a lateral and alongitudinal direction, etc.) and the engagement of the front chassislegs 480 with the ground surface 600 substantially prevents movement ofthe front end 12 of the surgical cart 10 (e.g., in a lateral and alongitudinal direction, etc.), thereby establishing complete immobilityof the surgical cart 10 (e.g., without locking the rear casters 302and/or the front wheels 202, etc.). In some embodiments, the brake pad424 and/or the front chassis legs 480 include a resilient material(e.g., rubber, etc.) to at least one of (i) increase the frictionbetween the brake pad 424 and/or the front chassis legs 480 and theground surface 600 and (ii) attenuate loads transferred from thesurgical cart 10 to the ground surface 600 (e.g., increasing thestability of the surgical cart 10, increasing the accuracy of thesurgical device 30, etc.). According to an exemplary embodiment, thefloor lock 400 does not lift the rear casters 302 of the surgical cart10 off of the ground surface 600. This may advantageously reduce theamount of force required to engage the floor lock 400 with the groundsurface 600 to immobilize the surgical cart 10 (e.g., as compared tolifting the rear end 14 of the surgical cart 10 off of the groundsurface 600 with the floor lock 400, etc.). The floor lock 400 appliesforce to the ground surface via the brake pad 424 thereby preventingmovement of the rear end 14 of the surgical cart 10. According to anexemplary embodiment, the front wheels 202 retract and/or the frontchassis legs 480 extend such that the front wheels 202 no longer touchthe ground surface 600 when the front chassis legs 480 engage the groundsurface 600 (e.g., free to rotate, completely unloaded, etc.).

Referring now to FIG. 5G, the floor lock 400, the carriage mount 320,and/or the carriage mount 370, along with the front chassis legs 480,provide a three-point support structure 500 for the surgical cart 10when the floor lock 400 is in the machining configuration 406. Optimumstability of the surgical cart 10 during use of the surgical device 30(e.g., when the surgical device 30 is moving, used in a procedure,machining, etc.) is achieved when the mass of the surgical cart 10 iskinematically supported by three points and the center of the mass islocated at the approximate centroid of an area defined by the threepoints. According to an exemplary embodiment, the surgical cart 10 issupported by the three-point support structure 500 which includes eachof the front chassis legs 480, the carriage mount 320, the carriagemount 370, and/or the brake pad 424 of the brake 420. Also, a center ofmass 510 of the surgical cart 10 is substantially near the centroid ofthe area defined by the three-point support structure 500. Therefore,the surgical cart 10 has three point stability when the floor lock 400is in the machining configuration 406 (i.e., increased stability whenstationary for machining) and quasi-four point stability (e.g., from thefront wheels 202 and the pivoting carriage assembly 300, etc.) when thefloor lock 400 is in the transportation configuration 402 (i.e.,increased stability when moving, prevents rocking, fluttering, andtipping during transport). According to an exemplary embodiment, thechassis 100 is relatively stiff to minimize deflection as loads aretransferred through the surgical cart 10 from the surgical device 30during operation (e.g., machining, etc.), further increasing theaccuracy of the surgical device 30.

In an alternative embodiment, the extension lever 460, the lift linkages470, the coilover 482, and/or the front chassis legs 480 are omitted. Inthe alternative embodiment, the carriage mount 320, the carriage mount370, and/or the floor lock 400, along with the front wheels 202, providea three-point support structure 502 for the surgical cart 10 when thefloor lock 400 is in the machining configuration 406 (e.g., withoutraising or lowering any portion of the surgical cart 10, the frontportion 110 of the chassis 100 may not kneel, etc.). Engaging the floorlock 400 may (i) lock the front wheels 202 in the current positionthereof or (ii) pivot and/or lock the front wheels 202 into a desiredpositon (e.g., a fore-and-aft positon, a lateral position, etc.). In oneembodiment, actuating the floor lock 400 orients and/or locks the frontwheels 202 in a longitudinal direction (i.e., forward). Longitudinallydisposing the front wheels 202 (as shown in FIGS. 5A-5B) may preventlateral movement of the front end 12, thereby establishing completeimmobility of the surgical cart 10. In another embodiment, actuating thefloor lock 400 orients and/or locks the front wheels 202 in a lateraldirection (i.e., sideways). Laterally disposing the front wheels 202 mayfurther prevent longitudinal movement of the front end 12 of thesurgical cart 10. In other embodiments, engaging the floor lock 400neither locks the front wheels 202 nor orients the front wheels 202 intoa desired position (e.g., the front wheels 202 may be manually pivotedinto a desired positon, the front wheels 202 may be manually locked,etc.). In some embodiments, the front wheels 202 include a brakemechanism positioned to rotationally fix the front wheels 202. In yetanother alternative embodiment, the surgical cart 10 includes one ormore floor locks 400 positioned at the front end 12 of the surgical cart10 to immobilize the front end 12 of the surgical cart 10. In a furtheralternative embodiment, the chassis 100 includes one or more rearchassis legs such that the surgical cart 10 is able to be lowered ontothe rear chassis legs (e.g., such that the front chassis legs 480 andthe rear chassis leg(s) immobilize the surgical cart 10, the frontwheels 202 and the rear chassis leg(s) immobilize the surgical cart 10,etc.).

Referring now to FIGS. 5A-5B, 6-9B, 11, and 13-17B, the wheel steeringassembly 200 is configured to facilitate maneuvering the surgical cart10 in a plurality of steering modes (e.g., fore-and-aft, turn-on-axis,lateral, etc.). As shown in FIGS. 5A-5B, 6, 7A, 8A, 9A, 11, 13-14B, 15B,16B, and 17B, the wheel steering assembly 200 includes a steering framemember, shown as steering swing arm 210. As shown in FIGS. 6-7A, 8A, 9A,11, 13-14B, 15B, 16B, and 17B, the steering swing arm 210 includes aplate, shown as steering plate 212; a wall, shown as wall 214, thatextends around a periphery of the steering plate 212; and a pair ofbrackets, shown as wheel brackets 216, coupled to the wall 214. Thewheel brackets 216 are configured to couple the front wheels 202 to thesteering swing arm 210. As shown in FIG. 7B, the front portion 110 ofthe chassis 100 defines apertures, shown as wheel apertures 116,positioned such that the wheel brackets 216 extended from the wheelapertures 116. Thus, the front wheels 202 are able to be positionedoutside of the chassis 100.

As shown in FIGS. 6-7A, 8A, and 9A, the steering swing arm 210 includesa pair of mounts, shown as steering assembly mounts 218. As shown inFIGS. 5A-5B, the steering assembly mounts 218 are configured to couplethe wheel steering assembly 200 to the chassis 100 within the innervolume 112. According to an exemplary embodiment, the middle portion 130of the chassis 100 defines a set of apertures that correspond withapertures defined by the steering assembly mounts 218. The correspondingapertures receive fasteners (e.g., nuts and bolts, etc.) which removablycouples the steering swing arm 210 to the chassis 100. According to anexemplary embodiment, the steering assembly mounts 218 pivotably couplethe steering swing arm 210 to the chassis 100 which thereby facilitatesthe rotation of the steering swing arm 210 as the front portion 110 ofthe chassis 100 kneels (e.g., when the floor lock 400 is engaged, etc.).

As shown in FIGS. 11, 13-14B, 15B, 16B, and 17B, the steering swing arm210 includes a pair of pivots, shown as steering assembly pivots 219,extending laterally therefrom. As shown in FIG. 11 , the middle portion130 of the chassis 100 defines a pair of mounts, shown as couplers 132,that are positioned to receive the steering assembly pivots 219. Thesteering assembly pivots 219 are thereby configured to couple the wheelsteering assembly 200 to the chassis 100 within the inner volume 112.According to an exemplary embodiment, the steering assembly pivots 219pivotably couple the steering swing arm 210 to the chassis 100 whichthereby facilitates the rotation of the steering swing arm 210 as thefront portion 110 of the chassis 100 kneels (e.g., when the floor lock400 is engaged, etc.).

As shown in FIGS. 6-7A, 8A, 9A, 11, and 13 , the wheel steering assembly200 includes a steering mechanism, shown as steering mechanism 240.According to an exemplary embodiment, the steering mechanism 240 isconfigured as a manually actuated mechanical linkage and/or crank systemthat steers the front wheels 202 in response to a manual actuation froman operator of the surgical cart 10. According to an exemplaryembodiment, the mechanical linkage and/or crank system of the steeringmechanism 240 eliminates the need for belts, gears, sprockets, and/oradjustments, thereby reducing costs and minimizing maintenance. In analternative embodiment, the steering mechanism 240 is anelectromechanical linkage system that is actuated by an actuator (e.g.,an electric motor, etc.) in response to receiving an command from thecomputing system 40 (e.g., a command based on an operator input receivedby the display device 42 or input device 44, etc.). In anotheralternative embodiment, each of the front wheels 202 and/or rear casters302 include an actuator (e.g., an electric motor, etc.) positioned tosteer each of the front wheels 202 and the rear casters 302independently in response to receiving a command from the computingsystem 40. In some embodiments, an electric motor is adapted to propelthe surgical cart 10 by providing rotational energy to at least one ofthe front wheels 202 and the rear casters 302.

As shown in FIGS. 5A-5B, 6-7A, 8A, and 9A, the steering mechanism 240includes a handle 242. The handle 242 is configured to provide anoperator of the surgical cart 10 with a lever to apply leverage in orderto reconfigure the steering mechanism 240 into the plurality of steeringmodes. As shown in FIGS. 5A-5B and 6 , the handle 242 is coupled to ashaft 244 which defines an axis, shown as rotational axis 241. By way ofexample, turning handle 242 about rotational axis 241 as indicated bydirectional arrow 243 may reconfigure the steering mechanism 240 into adesired steering mode.

As shown in FIGS. 5A-5B, 6, and 13 , the shaft 244 extends from thehandle 242 to an indexing member, shown as indexing case 246. In otherembodiments, the shaft 244 extends from one of the handgrips 52 to theindexing case 246. As shown in FIGS. 5A-5B, the indexing case 246 iscoupled to the chassis 100 (e.g., via a fastener, etc.). As shown inFIGS. 6-7A, 8A, 9A, and 13 , the indexing case 246 include a firstlinkage member, shown as rotational linkage 248, rotationally coupled tothe shaft 244 and disposed within the indexing case 246. The rotationallinkage 248 includes an extension, shown as retaining leg 247. Theretaining leg 247 is configured to abut the indexing case 246 to limitthe rotation of the rotational linkage 248 in a first direction (e.g.,clockwise, etc.) while allowing rotation of the rotational linkage 248in an opposing second direction (e.g., counterclockwise, etc.). Therotational linkage 248 also defines a plurality of indentations, shownas indicator indentations 249. Each indicator indentation 249 maycorrespond with an orientation of the handle 242 that is associated witha steering mode of the surgical cart 10. For example, a first indicatorindentation 249 may be associated with a fore-and-aft steering mode, asecond indicator indentation 249 may be associated with a turn-on-axissteering mode, and a third indicator indentation 249 may be associatedwith a lateral steering mode. According to an exemplary embodiment, asthe rotational linkage 248 rotates, the indicator indentations 249interact with a movable member (e.g., an indexer, a spring-loaded ballbearing, etc.) positioned within the indexing case 246 to provide anoperator with feedback (e.g., tactile feedback, etc.) that a presetsteering mode is engaged. The indicator indentations 249 may alsofacilitate holding the steering mechanism 240 in a desired one of thepreset steering modes (e.g., via the interaction between the indicatorindentation 249 and the moveable member, etc.).

As shown in FIGS. 6-7A, 8A, 9A, and 13 , the rotational linkage 248 iscoupled to a first end of a second linkage member, shown as connectinglinkage 250. As shown in FIGS. 6-7A, 8A, and 9A, an opposing second endof the connecting linkage 250 is coupled to a transfer member, shown astransfer block 252. The connecting linkage 250 is configured to transferthe rotational input provided by the rotational linkage 248 from thehandle 242 to the transfer block 252. As shown in FIGS. 7A, 8A, and 9A,the transfer block 252 is coupled to a first end of a pair of thirdlinkages, shown as intermediate linkages 256. Thus, the transfer block252 couples the connecting linkage 250 to the intermediate linkages 256.As shown in FIGS. 6-7A, 8A, and 9A, the transfer block 252 is slidablycoupled to a slide member, shown as linear slide 254. Thus, the transferblock 252 converts the rotational input from the handle 242 to a lineartranslation along the linear slide 254.

As shown in FIGS. 7A, 8A, and 9A, an opposing second end of each of theintermediate linkages 256 is coupled to a first end of a fourth linkage,shown as rotational linkage 258, and a first end of a fifth linkage,shown as driving linkage 260. As shown in FIGS. 6-7A, 8A, and 9A, anopposing second end of the rotational linkages 258 is rotationallycoupled to the steering plate 212. Thus, rotational linkages 258 rotateabout a point of connection between the opposing second end of therotational linkages 258 and the steering plate 212. As shown in FIGS.7A, 8A, and 9A, as the transfer block 252 is repositioned along thelinear slide 254 (e.g., by actuating the handle 242, etc.), theintermediate linkages 256 both rotate and translate, while therotational linkages 258 only rotate. Therefore, the movement of theintermediate linkages 256 is defined by the linear movement of thetransfer block 252 and the rotational movement of the rotationallinkages 258.

As shown in FIGS. 7A, 8A, and 9A, an opposing second end of the drivinglinkages 260 is coupled to a first end of a sixth linkage, shown aswheel linkage 262. An opposing second end of the wheel linkages 262 iscoupled to the front wheels 202. As the handle 242 is actuated, thedriving linkages 260 both rotate and translate causing the opposingsecond end of the driving linkages 260 to extend through the wheelapertures 116. The extension outwards from the wheel apertures 116 causethe wheel linkages 262 to rotate about a vertical axis, shown as wheelaxis 220 (shown in FIG. 6 ). Accordingly, the rotation of the wheellinkages 262 causes the front wheels 202 to rotate about the wheel axis220.

As shown in FIGS. 13-14B, 15B, 16B, and 17B, the opposing second end ofthe connecting linkage 250 is coupled to a crank mechanism, shown ascrank mechanism 700. As shown in FIGS. 14A-14B, 15B, 16B, and 17B, thecrank mechanism 700 includes a rotational synchronization element, shownas cam 710, a rotational element, shown as rotor 720, a pair oflinkages, shown as arms 730, and a pair of pivoting joints, shown aswheel joints 740. According to an exemplary embodiment, the rotor 720 isrotationally coupled to the steering plate 212 (e.g., with a rotationalbearing, etc.) of the steering swing arm 210. The cam 710 isrotationally fixed to the rotor 720 such that the cam 710 rotatestherewith, according to an exemplary embodiment.

As shown in FIGS. 14B, 15B, 16B, and 17B, the cam 710 defines a firstinterface, shown as connecting linkage interface 712, a secondinterface, shown as first arm connection interface 714, and a thirdinterface, shown as second arm connection interface 716. The opposingsecond end of the connecting linkage 250 couples to the connectinglinkage interface 712, a first end of a first arm 730 couples to thefirst arm connection interface 714, and a first end of a second arm 730couples to the second arm connection interface 716. As shown in FIGS.14A-14B, the cam 710 is spaced from the rotor 720 such that the firstend of the first arm 730 and the first end of the second arm 730 ispositioned therebetween. As shown in FIGS. 14B, 15B, 16B, and 17B, anopposing second end of the first arm 730 is coupled to a first wheeljoint 740 and an opposing second end of the second arm 730 is coupled toa second wheel joint 740. As shown in FIGS. 15B, 16B, and 17B, the wheeljoints 740 are pivotably coupled to the wheel brackets 216. Accordingly,the rotation of the wheel joints 740 causes wheel axles 203 and therebythe front wheels 202 to rotate about the wheel axis 220 (see FIG. 13 ).

As shown in FIGS. 15B, 16B, and 17B, movement of the connecting linkage250 (e.g., caused by the rotation of the handle 242, the handgrip 52,etc.) causes the cam 710 and the rotor 720 to rotate (e.g., about acentral axis thereof, etc.). Such rotation may drive the arms 730 toextend laterally outward (e.g., through the wheel apertures 116, etc.),thereby driving the wheel joints 740 to rotate within the wheel brackets216 to facilitate pivoting the front wheels 202 in various positions.According to an exemplary embodiment, the crank mechanism 700 (e.g., therotor 720, the cam 710, etc.) is laterally offset relative to alongitudinal centerline of the surgical cart 10 (e.g., laterally biasedtowards one side, etc.). According to an exemplary embodiment, the firstwheel joint 740 and the second wheel joint 740 have differentcharacteristics (e.g., shapes, dimensions, configurations, etc.).According to an exemplary embodiment, the cam 710 has an asymmetricshape. The lateral offset of the crank mechanism 700, the asymmetry ofthe cam 710, and/or the different characteristics of the wheel joints740 maintain the front wheels 202 in sync (e.g., the front wheels 202 donot pivot at different rates, angular rotation of the front wheels 202is synchronized, etc.).

According to an exemplary embodiment, actuation of the handle 242 and/orthe handgrip 52 corresponds with a 1:1 ratio of handle 242 and/orhandgrip 52 rotation to front wheel 202 rotation (i.e., an amount ofrotation of the handle 242 and/or the handgrip 52 directly correspondswith an amount of rotation of the front wheels 202). For example, a 45degree turn of the handle 242 and/or the handgrip 52 corresponds with a45 degree turn of the front wheels 202. In other embodiments, the amountof rotation of the handle 242 and/or the handgrip 52 does not directlycorrespond with the amount of rotation of the front wheels 202 (e.g., a1:2 ratio, a 2:1 ratio, a 1:3 ratio; a 3:1 ratio; etc.). According to anexemplary embodiment, the steering mechanism 240 isolates external loadson the front wheels 202 from the handle 242 and/or the handgrip 52. Inan alternative embodiment, the steering mechanism 240 steers the rearcasters 302 and the front wheels 202 are free to rotate. In anotheralternative embodiment, the steering mechanism 240 steers at least oneof the front wheels 202 and the rear casters 302. In yet anotheralternative embodiment, at least one of the front wheels 202 and therear casters 302 are able to be both steered and free to rotate (i.e.,the steering mechanism 240 is able to be selectively disengaged from thefront wheels 202 and/or rear casters 302).

According to the exemplary embodiment shown in FIGS. 7A-7B and 15A-15B,the surgical cart 10 is configured in a first steering mode, shown asfore-and-aft steering mode 270. As shown in FIGS. 7A-7B, the handle 242of the steering mechanism 240 is oriented in a first position, shown asfore-and-aft position 272, corresponding to the fore-and-aft steeringmode 270. As shown in FIG. 15A, the handgrip 52 is orientated in a firstposition, shown as fore-and-aft position 72. While the handle 242 isoriented in the fore-and-aft position 272 and/or the handgrip 52 isoriented in the fore-and-aft position 72, the front wheels 202 alignsuch that they are parallel with the longitudinal axis of the surgicalcart 10 (e.g., forward facing alignment, etc.). Thus, the surgical cart10 is able to be maneuvered by an operator in a conventional way such asin a forward direction or a reverse direction, as indicated bydirectional arrow 274. Also, the surgical cart 10 is able to turn whilemoving forward or backward while in the fore-and-aft steering mode 270since the rear casters 302 are free to rotate (e.g., about the verticalaxis 340, etc.).

According to the exemplary embodiment shown in FIGS. 8A-8B and 16A-16B,the surgical cart 10 is configured in a second steering mode, shown asturn-on-axis steering mode 280. As shown in FIGS. 8A-8B, the handle 242of the steering mechanism 240 is oriented in a second position, shown asturn-on-axis position 282, corresponding to the turn-on-axis steeringmode 280 (e.g., the handle 242 is turned approximately 45 degrees fromthe fore-and-aft position 272, etc.). As shown in FIG. 16A, the handgrip52 is oriented in a second position, shown as turn-on-axis position 82,corresponding to the turn-on-axis steering mode 280 (e.g., the handgrip52 is turned approximately 45 degrees from the fore-and-aft position 72,etc.). While the handle 242 is oriented in the turn-on-axis position 282and/or the handgrip 52 is oriented in the turn-on-axis position 82, thefront wheels 202 turn in towards the surgical cart 10 into a recess,shown as recess 114, defined by the front portion 110 of the chassis 100(e.g., at an angle of approximately 45 degrees relative to thelongitudinal axis of the surgical cart 10, etc.). Thus, the surgicalcart 10 is able to be maneuvered by an operator in a rotationaldirection, as indicated by directional arrow 284, about a central axis286 of the surgical cart 10. As shown in FIGS. 8A-8B and 16A, the rearcaster 302 rotate accordingly when the surgical cart 10 is maneuveredwhile in the turn-on-axis steering mode 280 to facilitate a zero radiusturn (i.e., the surgical cart 10 is rotatable in place about the centralaxis 286).

According to the exemplary embodiment shown in FIGS. 9A-9B and 17A-17B,the surgical cart 10 is configured in a third steering mode, shown aslateral steering mode 290. As shown in FIGS. 9A-9B, the handle 242 ofthe steering mechanism 240 is oriented in a third position, shown aslateral position 292, corresponding to the lateral steering mode 290(e.g., the handle 242 is turned approximately 90 degrees from thefore-and-aft position 272, etc.). As shown in FIG. 17A, the handgrip 52is oriented in a third position, shown as lateral position 92,corresponding to the lateral steering mode 290 (e.g., the handgrip 52 isturned approximately 90 degrees from the fore-and-aft position 72,etc.). While the handle 242 is oriented in the lateral position 292and/or the handgrip 52 is oriented in the lateral position 92, the frontwheels 202 turn completely into the recesses 114 such the front wheels202 are perpendicular to the longitudinal axis of the surgical cart 10(e.g., at a 90 degree angle to the longitudinal axis of the surgicalcart 10, etc.). Thus, the surgical cart 10 is able to be maneuvered byan operator in a lateral direction, as indicated by directional arrow294. As shown in FIGS. 9A-9B and 17A, the rear caster 302 rotateaccordingly when the surgical cart 10 is maneuvered while in the lateralsteering mode 290 to facilitate moving the surgical cart 10 laterally.Laterally maneuvering the surgical cart 10 may be useful followingmoving the surgical cart 10 (e.g., while in the fore-and-aft steeringmode 270, etc.) into a surgical operating room to position the surgicalcart 10 next to an operating table. Traditional surgical carts withfixed front wheels make this difficult. The cart has to be backed up,pivoted and moved back in. Sometimes this has to be repeated severaltimes until the position is correct. This often requires handling thecart from the front end which may be in a sterile field of the operatingroom, which is not ideal. The surgical cart 10 of the present disclosurefacilitates lateral translation at the operating table from the rear end14 of the surgical cart 10 in a non-sterile field of an operating room.Further, the pivoting carriage assembly 300 facilitates evenly loadingthe front wheels 202 for controlled lateral translation.

Referring back to FIGS. 7B, 8B, and 9B, in an alternative embodiment,the handle 242 of the steering mechanism 240 is omitted and one of thehandgrips 52 is mechanically coupled to the steering mechanism 240 toreconfigure the surgical cart 10 between the various steering modes (asdescribed above in regards to FIGS. 15A, 16A, and 17A). In anotheralternative embodiment, each of the handgrips 52 independently controlsthe rotation of the front wheels 202 (e.g., the right handgrip 52controls the pivoting of the right front wheel 202, the left handgrip 52controls the pivoting of the left front wheel 202, one rotates clockwiseand the other rotates counter-clockwise, etc.).

As shown in FIGS. 10, 15A, 16A, and 17A, the handgrip 52 (e.g., thatcontrols the rotation of the front wheels 202, etc.) includes a pushbutton, shown as lock button 56. In some embodiments, the lock button 56is configured to facilitate locking the rotational position of the frontwheels 202 (e.g., to prevent inadvertent rotation of the handgrip 52 andthe front wheels 202, etc.). In some embodiments, the lock button 56 isconfigured to facilitate unlocking the rotational position of the frontwheel 202 (e.g., a wheel lock for the front wheels 202 is biased into alocked position, etc.). In some embodiments, the position of the frontwheels 202 automatically locks in one or more positions (e.g., when thehandgrip 52 is oriented into the fore-and-aft position 72, etc.). Asshown in FIG. 15A, the handgrips 52 are angled relative to alongitudinal axis of the surgical cart 10 (e.g., angled fifteen degreesrelative to a longitudinal axis of the surgical cart 10, providing abetter ergonomic feel when pushing the surgical cart 10, etc.).

The steering mechanism 240 herein is described in detail as beingconfigured to facilitate selectively steering the front wheels 202between the fore-and-aft position 272, the turn-on-axis positon 282, andthe lateral position 292. However, it should be understood that thefront wheels 202 may be selectively pivoted between and/or locked at anyposition between the fore-and-aft position 272 and the lateral position292 (e.g., the front wheels 202 may be positioned and/or locked at anyangle between zero and ninety degrees relative to a longitudinal axis ofthe surgical cart 10, etc.).

The term “or” is used in its inclusive sense (and not in its exclusivesense) so that when used, for example, to connect a list of elements,the term “or” means one, some, or all of the elements in the list.Conjunctive language such as the phrase “at least one of X, Y, and Z,”unless specifically stated otherwise, is otherwise understood with thecontext as used in general to convey that an item, term, etc. may beeither X, Y, Z, X and Y, X and Z, Y and Z, or X, Y, and Z (i.e., anycombination of X, Y, and Z). Thus, such conjunctive language is notgenerally intended to imply that certain embodiments require at leastone of X, at least one of Y, and at least one of Z to each be present,unless otherwise indicated.

The construction and arrangement of the systems and methods as shown inthe various exemplary embodiments are illustrative only. Although only afew embodiments have been described in detail in this disclosure, manymodifications are possible (e.g., variations in sizes, dimensions,structures, shapes and proportions of the various elements, values ofparameters, mounting arrangements, use of materials, colors,orientations, etc.). For example, some elements shown as integrallyformed may be constructed from multiple parts or elements, the positionof elements may be reversed or otherwise varied and the nature or numberof discrete elements or positions may be altered or varied. Accordingly,all such modifications are intended to be included within the scope ofthe present disclosure. The order or sequence of any process or methodsteps may be varied or re-sequenced according to alternativeembodiments. Also two or more steps may be performed concurrently orwith partial concurrence. Such variation will depend on various factors,including software and hardware systems chosen and on designer choice.All such variations are within the scope of the disclosure. Likewise,software implementations could be accomplished with standard programmingtechniques with rule based logic and other logic to accomplish thevarious connection steps, processing steps, comparison steps anddecision steps. Other substitutions, modifications, changes, andomissions may be made in the design, operating conditions andarrangement of the exemplary embodiments without departing from thescope of the present disclosure.

What is claimed is:
 1. A surgical robot, comprising: a robotic arm; acart supporting the robotic arm and comprising a steering assembly;wherein: the steering assembly comprises wheels and a handle; the handleis moveable to a first position, a second position, and a thirdposition; and the steering assembly is configured such that: when thehandle is in the first position, the wheels allow the cart to roll in alongitudinal direction; when the handle is in the second position, thewheels allow the cart to roll in a rotational direction; and when thehandle is in the third position, the wheels allow the cart to roll in alateral direction.
 2. The surgical robot of claim 1, wherein thesteering assembly is configured such that: when the handle is in thefirst position, the wheels are parallel with a longitudinal axis of thecart; when the handle is in the second position, the wheels are angledrelative to the longitudinal axis of the cart; and when the handle is inthe third position, the wheels are perpendicular to the longitudinalaxis of the cart.
 3. The surgical robot of claim 1, wherein the wheelsare nonparallel when the handle is in the second position.
 4. Thesurgical robot of claim 1, wherein: the steering assembly furthercomprises a shaft; the handle is coupled to the shaft; and the handle isrotatable about an axis of the shaft to move between the first position,the second position, and the third position.
 5. The surgical robot ofclaim 4, further comprising an indexer coupled to the shaft andconfigured to provide tactile feedback when the handle reaches the firstposition, the second position, and the third position.
 6. The surgicalrobot of claim 5, wherein the indexer is configured to resist movementof the handle out of the first position, the second position, and thethird position.
 7. The surgical robot of claim 1, wherein the cartfurther comprises an additional wheel, wherein the additional wheel isfree to rotate about a vertical axis of the additional wheel.
 8. Asurgical cart, comprising: a body; and a steering assembly coupled tothe body, the steering assembly comprising wheels and a handle, wherein:the handle is moveable to a first position, a second position, and athird position; and the steering assembly is configured such that: whenthe handle is in the first position, the wheels allow the surgical cartto roll in a longitudinal direction; when the handle is in the secondposition, the wheels allow the surgical cart to roll in a rotationaldirection; and when the handle is in the third position, the wheelsallow the surgical cart to roll in a lateral direction.
 9. The surgicalcart of claim 8, wherein the steering assembly is configured such that:when the handle is in the first position, the wheels are parallel with alongitudinal axis of the surgical cart; when the handle is in the secondposition, the wheels are angled relative to the longitudinal axis of thesurgical cart; and when the handle is in the third position, the wheelsare perpendicular to the longitudinal axis of the surgical cart.
 10. Thesurgical cart of claim 8, wherein the wheels are nonparallel when thehandle is in the second position.
 11. The surgical cart of claim 8,wherein: the steering assembly further comprises a shaft; the handle iscoupled to the shaft; and the handle is rotatable about an axis of theshaft to move between the first position, the second position, and thethird position.
 12. The surgical cart of claim 11, further comprising anindexer coupled to the shaft and configured to provide tactile feedbackwhen the handle reaches the first position, the second position, and thethird position.
 13. The surgical cart of claim 12, wherein the indexeris configured to resist movement of the handle out of the firstposition, the second position, and the third position.
 14. The surgicalcart of claim 8, further comprising an additional wheel coupled to thebody and free to rotate about a vertical axes of the additional wheel.15. A steering assembly for a surgical cart, comprising: a shaft; ahandle coupled to the shaft and moveable to a first position and asecond position; and wheels operably connected to the handle via theshaft such that: when the handle is in the first position, the wheelsallow the surgical cart to roll in a first direction, wherein the firstdirection is a longitudinal direction, a lateral direction, or arotational direction; when the handle is in the second position, thewheels allow the surgical cart to roll in a second direction differentthan the first direction, wherein the second direction is thelongitudinal direction, the lateral direction, or the rotationaldirection.
 16. The steering assembly of claim 15, wherein the seconddirection is the rotational direction and the wheels are nonparallelwhen the handle is in the second position.
 17. The steering assembly ofclaim 16, wherein the first position is the longitudinal direction orthe lateral direction and the wheels are parallel when the handle is inthe first position.
 18. The steering assembly of claim 15, wherein thehandle is rotatable about an axis of the shaft to move from the firstposition to the second position.
 19. The steering assembly of claim 15,wherein the handle is further moveable to a third position and wherein,when the handle is in the third position, the wheels allow the surgicalcart to roll in a third direction different than the first direction andthe second direction.
 20. The steering assembly of claim 19, wherein thefirst direction is the longitudinal direction, the second direction isthe rotational direction, and the third direction is the lateraldirection.